Incident Overview
A pilot flying a single-engine aircraft experienced an engine malfunction while descending from 7,000 feet to 3,000 feet under clearance from Myrtle Beach Approach Control. According to the pilot's account, a "pop" sound was heard at approximately 6,000 feet, followed by rough engine operation and partial power loss. The engine monitor indicated that the No. 3 cylinder temperature gage read 900 degrees.
Emergency Response
The pilot immediately declared an emergency with the controller, reduced power, and requested clearance to the nearest airport. After receiving approval, the pilot executed a 180-degree turn and continued descending through cloud cover. Upon breaking out of the clouds into visual flight conditions, the pilot observed the airport directly ahead.
Forced Landing
The pilot descended over the airport to lose altitude and turned onto final approach. At approximately 300 feet above ground, the engine failed completely. The pilot initiated a forced landing to an open field; during the landing, the airplane collided with trees and the ground.
Examination and Findings
Post-accident examination of the engine assembly revealed that the No. 3 cylinder exhaust valve had fractured. The valve was sent to the NTSB Metallurgical Laboratory for detailed analysis. Metallurgical examination determined that the exhaust valve failed due to fatigue cracking resulting from thermal stress.